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Biomedical subjects

S Kamakura

Publications and source records attributed to S Kamakura.

At least 55 records · Page 3Linked to original sources
PubMed1999

Implanted octacalcium phosphate (OCP) stimulates osteogenesis by osteoblastic cells and/or committed osteoprogenitors in rat calvarial periosteum.

Our previous studies demonstrated that the octacalcium phosphate (OCP) causes new appositional bone formation on the OCP when implanted into the subperiosteal region of murine calvaria. The OCP may stimulate the cell population committed to the osteoblastic differentiation in the periosteum and have them express the phenotype. The present study was designed to investigate which periosteal cell population is involved in bone formation on the OCP with applying the OCP implants on top of and underneath the periosteum. The periosteum of the rat parietal bones was flapped and the OCP was implanted on top of or underneath the periosteum, in which the implantation sites were defined using the membrane filter. The histology was examined to see if new appositional bone formation occurs on the OCP implant under each condition. New bone was deposited on the OCP on the bone surface separated from the periosteum by the filter, whereas no bone was formed either under the periosteum separated from the bone surface by the filter or on the periosteum. The present study suggests that the OCP acts on osteoblasts, bone lining cells and/or their closely committed progenitors on the bone surface to express the phenotype and deposit new bone on the OCP implant.

Animals↗
PubMed1999

Confocal microscopy of dentinal tubules in human tooth stained with alizarin red.

The present study was designed to analyze the structures of dentinal tubules by confocal microscopy. Undecalcified ground sections of human teeth were stained with alizarin red in 0.1% KOH aqueous solution, and examined by confocal microscopy. Alizarin red stained dentinal tubules, interglobular dentine, granular layer of Tomes, and the surface of dentine. Interglobular dentine was seen between the outer and middle layers of coronal dentine. At the outer layer of coronal dentine, the dentinal tubules were thin and showed numerous branches. At the middle layer of coronal dentine, dentinal tubules displayed two types. The type I tubules are the dentinal tubules that do not show any nodular structures and the type II tubules are the dentinal tubules that appear bamboo-like with many nodules. In the cross section through the type II tubules, the nodules appeared as fine circular tubules surrounding the dentinal tubules. The circular tubules of nodules adhered to one side of the dentinal tubules. When the fluorescence images were compared with the images taken by transmission light mode, the fluorescence of dentinal tubules was seen at the inner surface of dentinal tubules, and the fluorescence of nodules was seen at interface between peritubular and intertubular dentine. Most of the dentinal tubules were of the type II tubules in the teeth from older individuals, whereas the type II tubules were scarce in the teeth from younger individuals. At the inner layer of coronal dentine, the dentinal tubules have no nodules and branches were scarce. The dentinal tubules of radicular dentine were different from those of coronal dentine. Most of the dentinal tubules were the type I tubules. Numerous fine branches were seen at the outer and middle layers of radicular dentine. No interglobular dentine was seen in the root except at the cervical part, and the granular layer of Tomes was also positive with alizarin red. At the cervical part of the root, interglobular dentine was present and the dentinal tubules displayed types I and II.

Adult↗
PubMed1999

Exercise-induced ST elevation in patients with arrhythmogenic right ventricular dysplasia.

To test the hypothesis that local or diffuse wall motion abnormalities in the right ventricle in patients with arrhythmogenic right ventricular dysplasia (ARVD) may induce the ST-segment elevation in response to exercise, we examined exercise electrocardiograms in patients with ARVD. In 17 patients with ARVD, who demonstrated right ventricular wall motion abnormalities without organic coronary lesions, we conducted a treadmill exercise test. Significant exercise-induced ST-segment elevation (ESTE) was defined as a 0.1 mV or more ST-segment elevation at J point. ESTE was observed in 11 patients (65%). It manifested most frequently in right-sided precordial leads. Severe right ventricular asynergy was seen in all but one (91%) among 11 with ESTE, whereas it was seen only in two (33%) among six without ESTE (P<.05). The maximal magnitude of ESTE inversely correlated with right ventricular ejection fraction (r = -0.58, P<.05). ESTE was seen in two thirds of ARVD patients, helping us noninvasively diagnose ARVD. The fact that ventricular wall motion abnormalities could cause ESTE in the absence of organic coronary lesions suggested the critical role of mechanical factors in the genesis of ESTE.

Adolescent↗
PubMed1999

The circadian pattern of the development of ventricular fibrillation in patients with Brugada syndrome.

AIMS: Brugada syndrome is considered to be a distinctive subgroup of idiopathic ventricular fibrillation. Identification of the circadian pattern of ventricular fibrillation would contribute to the elucidation of its underlying pathophysiology, but this pattern remains unknown in patients with Brugada syndrome. METHODS: and Results A total of 12 consecutive Brugada syndrome patients (46+/-14 years, all male) who underwent implantation of an implantable cardioverter defibrillator were studied. The distribution of the time of ventricular fibrillation detection was examined and classified into four 6-hour time periods of the day. The mean follow-up period following implantation was 777+/-535 days. In six out of the 12 patients, ventricular fibrillation occurred during follow-up. The data logs revealed that ventricular fibrillation was detected 30 times (range, 3-9). Ventricular fibrillation was observed more frequently at night ( 1800 h to 0600 h) than in the day (0600 h to 1800 h) (93.3% [28/30] vs 6.7%[2/30], P<0.001), and during sleep than while awake (86.7% [26/30] vs 13.3%[4/30], P<0.001). Ventricular fibrillation occurred most frequently between midnight and 0600 h in patients with ventricular fibrillation episodes during sleep (76.9% [20/26] vs 23.1%[6/26], P<0.01). CONCLUSION: These results suggest that increased nocturnal vagal activity and withdrawal sympathetic activity may play an important role in the arrhythmogenesis of the Brugada syndrome.

Adult↗
PubMed1999

Implantation of octacalcium phosphate (OCP) in rat skull defects enhances bone repair.

Synthetic octacalcium phosphate (OCP) enhances bone formation if implanted into the subperiosteal region of murine bone. Such implanted OCP may be resorbed and replaced by bone with time. We hypothesized that OCP could be used as an effective bone substitute. To test this hypothesis, we designed the present study to investigate if bone repair in a rat skull defect is enhanced by the implantation of OCP. Rats were divided into two groups: OCP-treated animals and untreated controls. Six rats from each group were fixed at 4, 12, and 24 weeks after implantation. A full-thickness standardized trephine defect was made in the parietal bone, and synthetic OCP was implanted into the defect. After being examined radiographically, the specimens were decalcified and processed for histology. OCP implantation significantly promoted bone repair compared with the controls. A statistical analysis showed an increase in the area of radiopacity within the skull defect between week 4 and week 12. Histologically, bone was formed on the implanted OCP and along the defect margin at week 4. At week 12, the implanted OCP was surrounded by newly formed bone. At week 24, the defect was almost completely filled with bone. In the control, bone formation was observed only along the defect margin. The present results demonstrate that OCP could be used as an effective bone substitute.

Animals↗
PubMed1998

Diagnostic value of plasma levels of brain natriuretic peptide in arrhythmogenic right ventricular dysplasia.

BACKGROUND: Arrhythmogenic right ventricular dysplasia (ARVD) is characterized by local or diffuse wall motion abnormalities in the right ventricle (RV), associated with recurrent ventricular tachycardia (VT) of RV origin. Brain natriuretic peptide (BNP) was first isolated from a porcine brain extract. In humans, BNP is expressed predominantly in the ventricles of failing hearts, and its expression has been observed primarily in myocytes in the interstitial fibrous area in dilated cardiomyopathy. We hypothesized that BNP is increasingly secreted from the residual myocytes within the atrophic tissue in patients with ARVD. METHODS AND RESULTS: Plasma BNP levels were measured in 17 patients with ARVD, 12 patients with idiopathic RV outflow tract tachycardia (RVOT), and 120 control subjects. We performed cardiac catheterization, RV endomyocardial biopsy, electron- beam CT, and biventricular endomyocardial mapping in the ARVD patients. There was a significant increase in plasma BNP levels in the ARVD patients compared with the RVOT patients and control subjects (61.4+/-59.6 pg/mL versus 8.3+/-5. 5 pg/mL and 9.3+/-5.8 pg/mL; P<0.0001, respectively). The plasma BNP levels had no correlation with any of the hemodynamic data, but they had a significant correlation with the RV ejection fraction (r=-0. 588, P=0.025) and with the fractionated-area scores (r=0.705, P=0. 005). Light microscopic immunohistochemistry showed strong BNP immunoreactivity in residual myocytes with fibrofatty replacement. CONCLUSIONS: These results suggest that plasma BNP levels were not increased in RVOT patients but were increased in ARVD patients, and that the increased BNP levels indicate the severity of both the RV dysfunction and the arrhythmogenic substrate.

Adolescent↗
PubMed1998

Clinical and electrophysiologic features of idiopathic left ventricular aneurysm with sustained ventricular tachycardia.

We examined 10 patients with idiopathic left ventricular (LV) aneurysm with sustained ventricular tachycardia (VT) (Id-An group), and compared them with those in 16 age- and sex-matched patients who had postinfarction aneurysm and VT (MI-An group) to clarify detailed clinical and electrophysiologic characteristics of idiopathic LV aneurysm. The clinical and laboratory data and results of electrocardiography, electrophysiologic, and morphologic examinations in the two groups were compared. In the Id-An group, the LV aneurysms were located more often at the posterior and/or inferior wall, while in the MI-An group, they were more often located at the anterior and/or apical wall (P<0.001). The LV end-diastolic volume index was significantly smaller and the LV ejection fraction was significantly higher in the Id-An group (P<0.001). The size of the aneurysm and the area with abnormal electrograms in the Id-An group were significantly smaller than those in the MI-An group (P<0.005 and P<0.001, respectively). The inducibility of VT was high in both groups, and ventricular pacing during VT showed entrainment phenomenon in most of the patients. Thus, in both groups, the abnormal electrograms were closely associated with the wall motion abnormality, and reentry was suggested as the mechanism of VT. In the Id-An group, since the lesions were anatomically and electrophysiologically confined to the posterior and/or inferior wall, the global LV function was more well preserved compared with the MI-An group.

Cardiac Catheterization↗
PubMed1998

Localization of optimal ablation site of idiopathic ventricular tachycardia from right and left ventricular outflow tract by body surface ECG.

BACKGROUND: Idiopathic ventricular tachycardia (VT) is known to arise from the right ventricular (RV) and left ventricular outflow tracts (LVOT). However, reliable noninvasive methods to localize the optimum ablation site for VT have not been reported. METHODS AND RESULTS: Body surface maps (BSM) and 12-lead ECGs were investigated in 35 VTs from the RVOT and 5 VTs from the LVOT in which the origin was confirmed during the ablation procedure. The RVOT was classified into 8 subdivisions with the use of a 3-dimensional anatomic relation: anterior (A) posterior (P), right (R) left (L), and superior (S) inferior (I). On the BSM, the following 3 indexes differentiated each location of the origin, with a diagnostic accuracy of 88% (A-P), 92% (R-L), and 77% (S-I): (1) the location of the minimum at the early-to-mid QRS (right, A; left, P), (2) the isopotential distribution in the left shoulder area after 30 ms of QRS (positive, R; negative, L), and (3) the downward moving time of the minimum at the early-to-mid QRS (>/=50 ms, S; <50 ms, I). On the 12-lead ECG, (1) the QRS duration (>140 ms, A; </=140 ms, P) and the R-wave pattern in leads II and III (RR' or Rr', A, R, P), (2) the QS wave amplitude in aVR and aVL (aVR>/=aVL, R; aVR /=1 in lead V3 was an index suggesting the LVOT origin. CONCLUSIONS: The origin or the optimum ablation site of idiopathic VT from RVOT and LVOT can be localized with the use of indexes obtained with a BSM or 12-lead ECG.

Adolescent↗
PubMed1998

Improvement of repolarization abnormalities by a K+ channel opener in the LQT1 form of congenital long-QT syndrome.

BACKGROUND: This study used monophasic action potential (MAP) to examine the effect of nicorandil, a K+ channel opener, on repolarization abnormalities induced by epinephrine in the LQT1 form of congenital long-QT syndrome in which the KvLQT1 mutation underlies the defect in the channel responsible for the slowly activating component of the delayed rectifier potassium current. METHODS AND RESULTS: MAPs were recorded simultaneously from two or three sites on the right ventricular and left ventricular endocardium in 6 patients with a congenital form of LQT1 syndrome with KvLQT1 defect (17 sites) and 8 control patients (24 sites). In LQT1 patients, epinephrine infusion prolonged the QT interval and 90% MAP duration (MAPD90) and increased the dispersion of MAPD90. Epinephrine also induced early after depolarizations (EADs) as well as ventricular premature complexes (VPCs) in 2 of the 6 patients. Nicorandil during epinephrine infusion abbreviated the QT interval and MAPD90, decreased the dispersion of MAPD90, and abolished the EADs as well as the VPCs in 1 patient. Addition of propranolol completely reversed the effect of epinephrine in prolonging the QT interval and MAPD90 and increasing the dispersion and eliminated the EADs and VPCs in another patient. In control patients, the effect of epinephrine and that of additional nicorandil and propranolol on repolarization parameters were much less than in the LQT1 patients. CONCLUSIONS: Our results suggest that nicorandil, a K+ channel opener, improves repolarization abnormalities in the LQT1 form of congenital long-QT syndrome with KvLQT1 defect.

Adolescent↗
PubMed1998

Application of tissue Doppler imaging technique in evaluating early ventricular contraction associated with accessory atrioventricular pathways in Wolff-Parkinson-White syndrome.

To examine the feasibility of a tissue Doppler imaging (TDI) technique for evaluating the early contraction sites in Wolff-Parkinson-White (WPW) syndrome, we analyzed the time-sequential changes in ventricular wall motion in WPW syndrome by TDI. Fifty patients with WPW syndrome were examined by the TDI system in which the high-speed scanning technique allowed for a frame rate up to 38 frames/sec. Among 42 patients in whom the acceptable images were obtained by TDI, the early contraction, which was represented by a red or blue spot appearing on the subendocardial side at the time of the delta wave in the electrocardiogram, was demonstrated in 25 of 29 patients with left-sided accessory pathways. However, in 13 patients with right-sided pathways, the early contraction sites could be identified in only five patients. The TDI-determined early contraction sites were well coincided with the sites of the accessory pathways determined by the electrophysiologic examination (p < 0.01). After the successful radiofrequency catheter ablation, early contraction sites were found to disappear by TDI in all patients. These results demonstrate the feasibility of the TDI technique to evaluate the early ventricular contraction associated with the atrioventricular accessory pathways. We suggest that the TDI system is helpful to localize the accessory pathways and to evaluate the results after radiofrequency ablation, although further studies are necessary to demonstrate the advantage of TDI over conventional echocardiography and electrophysiologic study in the evaluation of the accessory pathways in WPW syndrome.

Adolescent↗
PubMed1998

Morphologic changes in the elastic fibers of the temporomandibular joint after experimental disc perforation in the rabbit.

PURPOSE: Elastic fibers in the attachment regions of the temporomandibular joint (TMJ) are considered important in the movements of the disc during jaw motion. This study was designed to determine whether there are change in the elastic fibers of the TMJ when the disc is perforated for a long period. MATERIALS AND METHODS: Each TMJ of five rabbits was surgically exposed, and a mediolateral perforation was made in the center of the articulating region of the disc with a scalpel. Five untreated and three sham-operated rabbits were used as controls. The TMJs were removed after 10 months and processed for histochemical demonstration of elastic fibers. RESULTS: Osteoarthritic changes and a significant decrease in number of the elastic fibers in the anterior-inferior attachment and posterior-inferior attachment of the TMJ disc were observed after disc perforation. Conversely, elastic fibers appeared in the fibrous tissue on the resorbed bone of the articular eminence. CONCLUSIONS: Experimental disc perforation changes the distribution and density of the elastic fiber in the TMJ as well as causes osteoarthritis. A knowledge of these facts may improve our understanding of perforation of the disc.

Animals↗
PubMed1998

Radiofrequency catheter ablation of concealed atrioventricular accessory pathways using a "simultaneous pacing method".

The retrograde atrial potential at a successful ablation site is usually obscured by the wide and large ventricular potential during atrioventricular reentrant tachycardia or ventricular pacing, which makes it difficult to determine the appropriate ablation site for a concealed accessory pathway. A pacing maneuver named the "simultaneous pacing method" is proposed herein to differentiate the retrograde atrial potential from the ventricular potential for a successful ablation of the concealed accessory pathway. Catheter ablation was performed in 12 patients with a single left free-wall concealed accessory pathway. The atrial insertion site was determined by the simultaneous pacing method in six patients (group I) and by ventricular pacing in six patients (group II). In the simultaneous pacing method, electrograms recorded during ventricular pacing in the earliest retrograde atrial activation site are a fusion of the ventricular potential and the following retrograde atrial potential. When atrial and ventricular pacings are performed simultaneously (simultaneous pacing), the end portion of the electrograms recorded at the same site is solely the ventricular component, because atrial is activated earlier. The atrial potential can be confirmed during ventricular pacing in comparison with the electrograms during the "simultaneous pacing." Radiofrequency catheter ablation was successful in eliminating conduction through the accessory pathway in all 12 patients. The radiofrequency applications in group I were significantly fewer than those in group II (1.7 +/- 1.0 in group I, 5.3 +/- 3.2 in group II, P < 0.05). The total procedure time in group I was significantly shorter than in group II (57.8 +/- 15.7 vs 106.7 +/- 41.6 mins in group II, respectively, P < 0.05). The fluoroscopy time in group I was significantly shorter than in group II (54.0 +/- 7.9 vs 81.3 +/- 26.3 mins, respectively, P < 0.05). We were able to determine the atrial insertion site of accessory pathways by the simultaneous pacing method. The simultaneous pacing method was useful in eliminating concealed left free-wall accessory pathways.

Adult↗
PubMed1998

Mid-diastolic potential is related to the reentrant circuit in a patient with verapamil-sensitive idiopathic left ventricular tachycardia.

We report a case of verapamil-sensitive idiopathic ventricular tachycardia in which a mid-diastolic potential (MDP) 45 msec preceding the Purkinje potential (P potential) was recorded. Pacing during the tachycardia caused concealed entrainment, and the stimulus-QRS interval was equal to the P potential-QRS interval. The interval between the last pacing stimulus and the next P potential (postpacing interval) was longer than the ventricular tachycardia cycle length, but the MDP was orthodromically activated. These findings suggest that the MDP was on the reentrant circuit and the P potential was not on the reentrant circuit, but a bystander.

Adult↗
PubMed1998

Increased dispersion of repolarization time determined by monophasic action potentials in two patients with familial idiopathic ventricular fibrillation.

INTRODUCTION: The role of increased dispersion of repolarization in the genesis of torsades de pointes in patients with long QT syndrome has been clarified, but its role in the genesis of idiopathic ventricular fibrillation (VF) is not yet known. To investigate the pathogenesis of VF, we recorded monophasic action potentials (MAPs) from two siblings (48- and 36-year-old males) with familial idiopathic VF. METHODS AND RESULTS: The elder brother (patient 1) showed a late r' wave in lead V1 and ST segment elevation in leads V1 through V3. The younger brother (patient 2) had late r' waves and ST segment elevation in leads II, III, and aVF, and the configurations were very similar to those of patient 1. MAPs were recorded from several sites in the right ventricular (RV) and left ventricular (LV) endocardium during constant right atrial pacing. The repolarization time (RT) was defined as the sum of the activation time (AT) and action potential duration (APD) at 90% repolarization. In patient 1, marked prolongation of the AT (140 msec) and the RT (380 msec) was recorded in the RV septum of the outflow tract, and the RT dispersion was markedly increased (125 msec). In contrast, patient 2 showed prolongation of the AT (80 msec) and RT (310 msec), and fractionated electrograms in the RV floor of the inflow tract. The RT dispersion was also increased (80 msec). VF and nonsustained polymorphic ventricular tachycardia were induced by double premature stimulation in patients 1 and 2, respectively. Chronic amiodarone therapy decreased the RT dispersion and suppressed the induction of ventricular tachyarrhythmias in patient 2, although late r' waves and slight ST segment elevation were unmasked in leads V1 and V2. CONCLUSION: Our data suggest that the increased dispersion of the RT, which was due mainly to a localized conduction delay in the RV, created an arrhythmogenic substrate in the two patients with familial idiopathic VF.

Action Potentials↗
PubMed1998

Dynamic changes of 12-lead electrocardiograms in a patient with Brugada syndrome.

We present a patient with Brugada syndrome in whom 12-lead ECGs were recorded just before and after an episode of ventricular fibrillation (VF). A progressive elevation of both the RS-T segment and J waves just preceding and following the VF, and a close relationship between the amplitude of the RS-T segment and the preceding R-R intervals during atrial fibrillation, were documented. These findings support the hypothesis that RS-T elevation and a subsequent VF are related to a transient outward current-mediated spike-and-dome morphology of the epicardial action potential.

Adult↗
PubMed1998

Epithelial rests colocalize with cementoblasts forming acellular cementum but not with cementoblasts forming cellular cementum.

Epithelial rests of Malassez and cementoblasts were examined in the rat molars during the early stages of root formation using an antilaminin antibody and/or peanut agglutinin (PNA), and an antiosteocalcin (OC) antibody, respectively. The roots of the first molars were used for study. The antilaminin antibody stained the basement membrane surrounding the epithelial root sheath and epithelial rests. The basement membrane of the epithelial root sheath was continuous, but that of the epithelial rests was discontinuous. The cells of epithelial rests and epithelial root sheath were positive for PNA. The structural characteristics of the epithelial rests were seen in the sections stained doubly with PNA and the antilaminin antibody. The cells of epithelial rests were fibroblast-like and formed a fine mesh in 2-week-old rats. In 3-week-old rats, the epithelial rests were also present at the coronal half of root surface, showing typical cell cords, but were not present at the apical part of the root surface where the cellular cementum covered the root dentin. At the root apex of 3-week-old rats, the cells of epithelial rests forming fine meshes were seen near the epithelial root sheath. The anti-OC antibody stained cementoblasts lining acellular and cellular cementum. The sections doubly stained with the anti-OC and the antilaminin antibodies or PNA further revealed the close relation between epithelial rests and cementoblasts. The OC-positive cells lining acellular cementum or dentin were localized very close to the epithelial rests. In contrast, the OC-positive cells lining cellular cementum did not show close association with the epithelial cells, except the cells located most apically where the basement membrane of the epithelial root sheath is disrupted and the initial cellular cementum begins to be formed. The present results suggest that the epithelial rests and/or the discontinuous basement membrane of them may have a role for the acellular cementum formation at least in the early stage of root formation.

Animals↗
PubMed1997

Cloning and characterization of the 5'-flanking region of the human dopamine D4 receptor gene.

Dopamine D4 receptor (DRD4) has received attention in terms of pathogenesis of schizophrenia and association with human personalities. We isolated the human DRD4 gene containing the 5'-flanking region and determined its sequence. Analysis of the DRD4 transcripts by 5'-RACE (5'-rapid amplification of cDNA ends) revealed a region of the transcription initiation located between -501 and -436 relative to the first nucleotide of the initiation codon. There is a CpG island spanning from -900 to +500 but no TATA or CAAT boxes in the 5'-flanking region. Functional analysis of the 5'-flanking region of the DRD4 gene by a transient expression method revealed the presence of a negative modulator between -770 and -679. The region between -591 and -123 gave the highest transcriptional activity in IMR32 (neuroblastoma) and Y-79 (retinoblastoma) cells but not in HeLa cells, suggesting that this housekeeping gene-like promoter regulates the cell-type specific gene expression.

Base Sequence↗